1. Field of Invention
The invention relates to a color ink jet recording apparatus, and more particularly, to an ink jet recording apparatus that includes ink cured by irradiation of energy, a plurality of ink jet heads provided for each kind of ink for color printing and an energy generating device that irradiates a recording medium with energy for curing the ink.
2. Description of Related Art
Ink jet recording apparatuses that perform a printing operation using radiation curing type ink have been known. For example, Japanese Laid-Open Patent Publications No. 60-132767, No. 7-224241 and No. 8-21808 disclose related technologies.
Japanese Laid-Open Patent Publication No. 60-132767 discloses an ink jet recording apparatus that includes an ink jet head that ejects ink droplets of ultraviolet curing type ink onto a recording medium to print characters and the like in a dot matrix and an ultraviolet lamp that irradiates a portion where the characters and the like are printed on the recording medium with ultraviolet light.
Japanese Laid-Open Patent Publication No. 7-224241 discloses an ink jet recording apparatus that includes four ink jet heads for ultraviolet (UV) curing type inks, yellow (Y), magenta (M), cyan (C) and black (Bk) inks, and can record an image in full color with a single scan. A plurality of recording mediums are loaded in a stocker. The recording sheets are fed, one by one, to a belt conveyor by a conveyor, and then fed to a printing tray. At a first step, surface wettability of the recording medium is increased using a UV/O3 lamp. Then, at a second step, printing operation is performed using the ink jet heads. At a third step, the recording medium is irradiated with ultraviolet light (hereinafter, referred to as a first apparatus).
In a modified ink jet recording apparatus disclosed in Japanese Laid-Open Patent Publication No. 7-224241, a Y head, an M head, a C head and a Bk head are disposed along a recording medium feeding path, in order, at regular intervals. An ultraviolet lamp is provided between each head and on a recording medium discharging side of the Bk head. Every time printing of one color is completed, a printed portion is irradiated with ultraviolet light (hereinafter, referred to as a second apparatus).
An ink jet recording apparatus disclosed in Japanese Laid-Open Patent Publication No. 8-21808 has a similar structure to that disclosed in Japanese Laid-Open Patent Publication No. 7-224241.
The ink jet recording apparatus disclosed in Japanese Laid-Open Patent Publication No. 60-132767 performs printing in monochrome, not in polychrome.
The ink jet recording apparatuses disclosed in Japanese Laid-Open Patent Publications No. 7-224241 and No. 8-21808 can perform printing in polychrome.
However, in the first apparatus, the recording medium is irradiated with the ultraviolet light only after printing in the four colors of inks, the Y, M, C and Bk inks, is completed, thereby causing the following problems. The UV curing type ink is cured only after the ink is irradiated with the ultraviolet light. Accordingly, the different colors of the inks may mingle before the inks are cured. If it happens, the colors of the inks cannot be clearly represented on the recording medium.
In the second apparatus, first, printing is performed on the entire recording medium using one color of the ink, and then the entire recording medium is irradiated with ultraviolet light. After that, printing is performed on the entire recording medium using another color of the ink, and then the entire recording medium is irradiated with the ultraviolet light. By doing so, unclearness or dullness of the colors of the inks on the recording medium due to the intermixture of the different colors of inks cannot occur. However, in this second apparatus, printing is performed on the entire recording medium using one color of the ink, and then the entire recording medium is irradiated with ultraviolet light. This series of operation is repeated with respect to each color of the ink. Accordingly, it takes much too long to print the entire recording medium with the four colors of inks. In addition, this apparatus becomes large in size.
The invention provides an ink jet recording apparatus that performs recording using different kinds of inks that are cured by irradiation of energy, wherein the time required for printing is shortened and colors of the inks can be clearly represented without upsizing the ink jet recording apparatus.
The ink jet recording apparatus according to an embodiment of the invention includes a plurality of ink jet heads, each of which ejects ink droplets of a different kind of ink that can be cured by irradiation of energy toward a recording medium, a carriage that is movable with respect to the recording medium in a main scanning direction and in a sub scanning direction perpendicular to the main scanning direction with the ink jet heads mounted on the carriage and aligned in the sub scanning direction, a movement generating device that moves the carriage with respect to the recording medium, a print control device that controls the ink jet heads and movement generating device so that the ink droplets ejected from each of the ink jet heads overlap each other on the recording medium by performing ejection of ink using the ink jet heads while moving the carriage with respect to the recording medium in the main scanning direction and by moving the recording medium in the sub scanning direction by a predetermined amount with respect to the carriage after every ejection of ink done during one way or two way moving of the carriage in the main scanning direction is performed, and an energy generating device that irradiates the recording medium with energy for curing the ink droplets ejected on the recording medium by the ink jet heads so that a printed portion of the recording medium formed by one of the ink jet heads during one reciprocation of the carriage in the main scanning direction is irradiated, at least once, before another of the ink jet heads ejects the ink droplet to a portion of the recording medium which is same portion as the printed portion formed by one of the ink jet heads.
According to the ink jet recording apparatus of the invention, the print control device moves the recording medium in the sub scanning direction with respect to the carriage after every printing is performed by moving the carriage in the main scanning direction with respect to the recording medium. The plurality of ink jet heads are aligned in the sub scanning direction perpendicular to the main scanning direction, on the carriage that can move in the main scanning direction with respect to the recording medium. For example, a yellow (Y) ink jet head, a magenta (M) ink jet head, a cyan (C) ink jet head and a black (K) ink jet head are aligned in this order in the sub scanning direction, on the carriage. In this case, an end of the recording medium in the sub scanning direction is located in a position opposite to the Y head. First, the carriage is moved in the main scanning direction with respect to the recording medium to perform printing using the Y head. Then, a portion printed in the Y ink is cured by irradiation of energy from the energy generating device.
The printed portion is an area that is to be formed by printing performed by the movement of the carriage in the main scanning direction with respect to the recording medium. The printed portion is defined by an amount of travel in the main scanning direction of the ink jet heads via the carriage and a width of ink ejection by a plurality of nozzles formed in the ink jet heads. The amount of travel in the main scanning direction of the ink jet heads is equal to a length of the printed portion in the main scanning direction (a printed length of the recording medium). The width of the ink ejection is equal to a length of the printed portion in the sub scanning direction. The printed portion defined as described above is referred to as one-line printing.
Next, the recording medium is moved in the sub scanning direction with respect to the carriage by the length of the printed portion in the sub scanning direction formed by one-line printing. As a result, printing can be performed using the Y and M heads this time. At that time, ink droplets to be ejected from the M head are ejected onto the Y ink that has already cured. Accordingly, the Y ink and the M ink do not intermix, so that the colors of the inks can be clearly represented. Next, the recording medium is moved in the sub scanning direction with respect to the carriage by the length of the printed portion in the sub scanning direction formed by one-line printing. This time, printing is performed using the yellow, magenta and cyan ink jet heads. At that time, also, ink droplets to be ejected from the M and C heads are ejected onto the other colors of inks that have already cured. Accordingly, the different colors of inks do not intermix, so that the colors of the inks can be clearly represented. Next, the recording medium is, again, moved in the sub scanning direction with respect to the carriage by the length of the printed portion in the sub scanning direction formed by one-line printing. This time, printing is performed using the Y, M, C and K heads. At that time, also, ink droplets to be ejected from the M, C and K heads are ejected onto the other colors of inks that have already cured. Accordingly, the different colors of inks do not intermix, so that the colors of the inks can be clearly represented. After that, this operation is repeated, and thus printing can be performed on the entire recording medium in color.
According to the ink jet recording apparatus, as described above, the ink jet heads are aligned in the sub scanning direction on the carriage and the print control as described above is performed. Therefore, the time required for printing in this apparatus is almost the same as or shorter than that required in an ink jet recording apparatus that performs printing in monochrome. In addition, the ink jet heads for such as the M, C and K inks, are mounted on the carriage, so that the ink jet recording apparatus does not become large in size. Further, registration of the recording medium between the ink jet heads is unnecessary for every printing in each color of ink, though it is required every printing in each color of ink in the second apparatus. Consequently, occurrence of displacements of colors or out-of-register colors can be minimized.